Froth flotation of oxidized ores



Patented Sept. 25, 1934 UNITED STATES PATENT ormcs No Drawing. Application January 21, 1932,

Serial N0. 588,031

19 Claims. (01. 209-166) Most of the methods heretofore used for the flotation of oxidized ores have included the addition of soluble sulfids, such as sodium sulfid, designed to place a sulfid film on the particles of oxidized minerals, together with the addition of the same collecting and frothing agents as are commonly used in the flotation of sulfid ores. Sulfidizing operations, however, are impractical on 20 many oxidized ores, because of the mineral depressing action evident when enough sulfidizing agent is added to produce effective filming, that is, too much sulfidizing agent will produce a barren froth, but on the other hand too little results in incomplete filming.

A further factor that strongly militates against the use of sulfidizing operations'in connection with ores containing appreciable quantities of oxidized minerals is the quick taking up of the reagent by the'sulfid components leaving an insufiicient quantity for the oxidized components with the consequent loss of the latter, furthermore oxidized ores containing much hydrated iron oxide or manganese oxide consume so much sulfidizing agent before filming of the valuable mineral is complete, that many of the valuable minerals become depressed by reaction products, such as sulfites.

Efforts to float the oxidized minerals by using, as reagents, the fatty acids, such as oleic acid, result in the flotation of many undesirable minerals, such as barite and calcite, and produce a froth so non-selective that good extraction and high grade concentrate are impossible of simultaneous attainment: one must be sacrificed for the other.

The-present invention is based on the dis covery that when chosen organic compounds are allowed to react with phosphorous pentasulfid in the presence of ammoniaythe reaction product is a direct effective flotation agent, not only for the sulfid minerals, but also for the oxidized minerals of gold, silver, lead, and copper, without the use of sulfidizing. agents, when used in non-' alkaline ore pulps to which has been added a suitable reagent such as sodium silicate for flocculation of the valuable minerals and dispersion of the gangue. In the preparation of these reaction products, the ammonia may be present as anhydrous gas, as aqua ammonia, or in combination with organic compounds,such as the amino compounds, aniline, toluidine, naphthylamine. Organic substances such as coal tar creosotes, petroleum oils, acetic acid, oleic acid, benzyl chloride, and alcohols, when allowed to'react with phosphorus pentasulfld in the presence of ammonia produce reaction products that directly promote the entry of the oxidized minerals into the froth and so avoid the disadvantages occurring with the use of sulfid filming.

The reagent is most effective when produced at a temperature below that caused by the heat reaction, action being slight at 25 (3., slow at 30 C., but brisk at 35 to 40 C., consequently the use of higher temperatures should be avoided it! as they tend to produce a reagent having inferior collecting quality because of the loss of sulfur by the excessive giving off of the hydrogen sulfid gas. Continuous stirring is desirable until all vigorous reaction, as evidenced by the so evolution of hydrogen sulfid gas, has ceased. To" produce a uniform product, the pasty reaction product should then be stored for several days at about 25 to 30 C., during which eriod the phosphorus pentasulfid gradually reacts com- 95 pletely as can be noted by the constantly decreasing production of the hydrogen sulfid gas.

To aid in uniformly feeding the pasty reagent to the flotation pulp, it is desirable to dilute it with an alcoholic solvent, and/or to render it water-soluble by the addition of an alkali or a non-oxidizing acid, such as sulfuric acid. If an alkali is used to render the reagent water soluble, it is usuallynecessary to add an acid to the ore pulp to produce effective flotation of oxidized minerals. If an acid is used to render the reagent water-soluble, the solution will be effective without theaddition of acid to the ore-pulp, provided theore-pulp itself is not alkaline. The acid soluble reagent permits better flotation conm trol, but must be fed by acid-proof equipment.

In an ore pulp containing both sulfid and oxidized minerals, stage addition of reagent is necessary to insure satisfactory recovery of oximinerals. It will be foundthat the sulfid minerals avidly consume the first reagent added, leaving little reagent to promote the entry of oxidized minerals into the froth. As most of the sulfid minerals will be removed dln'ing the first stage, the second addition of reagent will no float a larger proportion of oxidized mineral. After .two reagent stages, the froth will carry mineral that is almost entirely oxidized, usually from four to six stages of reagent addition will be required to efiect a nearly'compl'ete extraction of the valuable minerals.

It is advisable to carry out the operation in an ore pulp in which the valuable minerals are flocculated and the gangue is dispersed, soluble silicates, such as sodium silicate or silicic acid, being effective for this purpose. If an alkaline soluble silicate is used, care must be taken that the ore pulp is not rendered alkaline by its addition. The maintenance of proper hydrogen-ion concentration, by pH measurements and control, aids' most materially in the securing of best results. The pH value should not greatly exceed 7.0 at any time, and at the end of the flotation operation it should approach the optimum value of 5.4 for best results.

As specific examples of the manufacture and use of such a reagent, the following manipulation and results are given.

Example A To parts by weight of denatured alcoho 15 parts or percent. normalbutyl alcohol, and 36 parts aqua ammonia,-was slowly added 34 parts by weight or percent of phosphorous pentasulfid. The mixture was constantly stirred at a temperature of 40 C. until evolution of hydrogen sulfid gas had ceased.

A sample of Tintic Standard oxidized lead ore was ground to 70% thru 200 mesh, and floated with six stages of reagent addition as follows:

In a suitable mixer, in any order, were placed 25 lbs. of ethyl alcohol denatured by formula #5, 25 lbs. normal butyl alcohol, lbs. aqua ammonia and 25 lbs. of orthotoluidine, these producing no heat as no action occurs. While these chemicals were being stirred lbs. of phosphorus pentasulfid broken to lumps not larger than 10 mesh was very slowly added. At first no gaswas given off probably because this product of the reaction was absorbed by the alcohols present but after a while the gas was given off and the temperature tended to rise but was held to a figure below 40 C. during all of the hour or so required to add the sulfid sufliciently slowly as not togenera'te'the gas too fast and thus prevent foaming and 'con-' sequent loss of the mixture. i

The product, which was brownish-black when mixed in an iron kettle but grey when mixed in a copper machine, was pasty but could be poured into unsealed metal drums or other containers for storage so that the particles of phosphorus pentasulfld which visually had not yet reacted could be completely taken up, this requiring from four to flve days, altho two to three weeks are preferable as the last of the raw toluidine seems to react quite slowly and longer storage than a few days definitely increases the solubility in either acid or alkaline product and some sulfid gas is given off for at least a full week.

When ready for use one part of the reaction product so made was added to 9 parts of water and to this diluted agent was slowly added with constant stirring and without excessive heat increase, three tenths of a part of a strong nonoxidizing mineral acid, this being sulfuric acid in preference to hydrochloric because of the economy and ease of handling the former which dissolved 98% of the reagent leaving about two percent as a black residue that remained in suspension. As seen from the table below, the reagent was added in equal amounts per stage, altho this is not necessary or even usual, but the total quantity is generally between l /2 and 2 pounds per ton of the ore, and the sodium silicate which was added to the pulp in the same cell was increased by 50% in the second stage only. Sometimes the use of silicate is omitted in the first'stage. The quantity used is less than suflicient completely to disperse or deflocculate the gangue and never enough to muddy the tailing overflow after it is allowed to settle, this silicate not only clearing the color of the bubble but also rendering it more brittle.

In the example, the flotation machines were divided into four cells per stage..and the reagent and the silicate were added separately but simultaneously, to the first cell of each stage in succession. While not necessary with ores containing pyrites, which may produce a natural pH of 6.6, I added strong sulfuricv acid to the scoop box of the ball mill to bring the pH to about 6.8 as this greatly increases the efllciency. The acid which was added to the reagent could also be added here but I find that I can secure far better control by adding it directly to the reagent. The use of ammonia water as a source of ammonia not only is economical but is highly advantageous as it will not pick up barite, calcium carbonate, magnesium carbonate, etc.

A sample of highly oxidized Tintic Standard lead ore containing much pyrite was ground to thru 200 mesh, and floated with six stages of the acid soluble reagent as follows:

It will be understood that the foregoing are only examples of procedure, and I do not wish the invention to be limited to those specific agents or methods.

The degree of frothing can be controlled by selection of the proper kinds and amounts of alcohol used. Ethyl and propyl alcohols tend to produce no froth, whereas butyl and amyl alcohols have decided frothing qualities when reconstructed as shown.

What I claim is:

1. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, and ammonia, with sulfur and phosphorus.

2. The process of concentrating by froth flotation of ores containing oxidized minerals which 1 comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, and ammonia, with phosphorus pentasulfid.

3. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, aqua ammonia and phosphorus pentasulfld.

4. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an oxygen free aromatic amino compound, alcohol, ammonia, sulfur and phosphorus.

5. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, and ammonia, with sulfur and phosphorus in a non-alkaline circuit.

6. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, and ammonia, with phosphorus pentasulfld in a non-alkaline circuit.

'7. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an organic amino compound, alcohol, aqua ammonia and phosphorus pentasulfid in a non-alkaline circuit.

8. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of an oxygen free aromatic amino compound, alcohol, ammonia, sulfur and phosphorus in an acid circuit.

9. The process of concentrating by froth flotation of ores containing oxidized minerals which comprises subjecting the ore in the form of a pulp to a flotation operation in the presence of the reaction product of toluidine, alcohol, ammonia, and phosphorus pentasulfid.

10. An agent for use in flotation comprising the reaction product of an organic amino compound, ammonia, alcohol, sulfur and phosphorus.

11. An agent for use in flotation comprising the reaction product of an organic amino compound, alcohol, ammonia, phosphorus pentasulfid. v

12. An agent for use in flotation comprising the reaction product of an organic amino compound, alcohol, ammonia, water, sulfur and phosphorus.

13. An agent for use in flotation comprising the reaction product of an oxygen free aromatic amino compound, alcohol, ammonia, and phosphorus pentasulfid.

14. An agent for use in flotation comprising the reaction product of toluidine, alcohol, ammonia, and phosphorus pentasulfid.

15. The process of concentrating oxidized ores by froth flotation which comprises subjecting the ore in the form of a pulp having an acid reaction to a flotation operation in the presence of sodium silicate, and the reaction product of a mixture of ethyl and a higher alcohol, toluidine, and ammonia, with phosphorus pentasulfid. to which reaction product, after thorough mixture, storage, and dilution with water, a quantity of sulfuric acid has been added. a

16. The step in the process of concentrating by froth flotation of oxidized ores by the use of a cold-reaction product of an alcohol, and amino compound, phosphorus and sulphur which consists in adding acid to the pulp prior to the addition of the reconstructed reagent and also with the addition of the reagent, bringing the pH of the pulp to a point below 6.8.

17. The step in the process of concentrating oxidized ores by the use of a cold-reaction product of an alcohol, and amino compound, phosphorus and sulphur by froth flotation which consists in adding to the acid pulp at the time of the addition of the suitable reagent and in the same cell of a quantity of an alkaline silicate, and a sufficient quantity of acid to neutralize the alkaline condition produced by the silicate.

18. The step in the process of concentration by froth flotation of oxidized ores by the use of a cold-reaction product of an alcohol, and,

amino compound, phosphorus and sulphur which consists in adding acid to the pulp prior to the addition of the reconstructed reagent, and also with the addition of the reagent bringing the pH of the pulp to a point lower than 7.0 and maintaining the pH below said point throughout the operation and by reduction of the pH value to 5.4 at the end of the flotation operation.

19. The step in the froth flotation of oxidized ores conducted by the use of a cold-reaction product of an alcohol, an amino compound, and phosphorus pentasulfld, and by the use of sodium silicate, which consists in first adding to the pulp an acid to bring the pulp to a non-alkaline condition before flotation, and in adding successive charges of acid to the pulp during flotation to produce successively lower pH values.

GEORGE H. WIGTON. 

